I propose to study the sensitivity of the waxy (wx) locus of the angiosperm, Zea mays, to known chemical mutagens/carcinogens. The unit of measurement is the maize microgametophyte (pollen grain). Populations of 10 to the 6th power per test are easily scored with this system. Experiments on forward mutation and reverse mutation will be conducted with four agents. Three of these agents are carcinogens, ethyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, 3,6-bisdimethyl-aminoacridine HCl and the mutagenic herbicide, sodium azide. The genetic effects of four wx heteroalleles (mutational sites) will be analyzed. The heteroalleles are wx-H21, wx-C, wx-B, and wx-90. In addition, recombinogenic responses to each agent will be determined by treating plants that possess a different wx-heteroallele on each homologous chromosome 9. Intragenic recombination will be detected by scoring for functional Wx recombinant pollen grains. The experiments on the effects of the carcinogens/mutagens on the frequencies of mutation and intragenic recombination will be conducted with an acute and chronic treatment regime. Finally, I propose to use the data obtained by this research to construct a series of rapidly-maturing lines of maize with the appropriate genotypes that could function as monitors for genotoxins. Such environmental monitors could detect and prevent serious health hazards before such hazards could be studied epidemiologically.